Thermoplastic polymer alloy compositions have been developed to replace polyvinyl chloride for the fabrication of many articles. In the automotive field, thermoplastic polymer alloy compositions have been used for the fabrication of articles such as interior sheathing, including instrument panel skins, door panels, air bag covers, roof liners, and seat covers.
For example, U.S. Pat. No. 5,206,294 discloses a blend of polypropylene, ethylene copolymer ionomer resin, ethylene glycidyl acrylate or methacrylate copolymer, and uncrosslinked ethylene propylene rubber. U.S. Pat. No. 5,721,314 discloses a blend of polypropylene, ethylene copolymer ionomer resin, ethylene glycidyl acrylate or methacrylate copolymer, uncrosslinked ethylene propylene rubber, acid or anhydride grafted polypropylene, an agent for crosslinking the rubber and/or catalyzing an epoxide/acid reaction, and optionally, a poly-.alpha.-olefin. These compositions provide some of the low temperature and high temperature resistance properties and scuff resistance that are desired in automotive interior sheathing applications. However, they exhibit a shiny, high gloss appearance that is objectionable in such applications, thus requiring painting to achieve an acceptable appearance.
Thermoplastic polymer alloy compositions currently available also do not provide sufficient scuff and scratch resistance properties. Therefore, current fabrication practice requires painting skins (sheets) of thermoplastic polymer alloys before thermoforming the desired article from the painted skins in order to provide adequate scuff and scratch resistance to the formed article. The painting process can be expensive with respect to both labor and materials.
The current fabrication process includes the steps of melt blending and pelletizing a thermoplastic polymer alloy composition. The formed pellets are then fed into an extruder to form sheets of the pellets. The processing steps continue with embossing the sheets, applying a primer on a bottom surface of the sheet, heat curing, applying a primer on a top surface of the sheet, heat curing again, applying a top coat and heat curing again. After this laborious process, the primed, painted sheets can then be used to form articles of manufacture such as interior vehicle sheathing.
There is a need in the art for a thermoplastic polymer alloy composition having improved scuff and scratch resistance, high melt strength, and low gloss and gloss uniformity after thermoforming, color match and retention of color over time. There is a further need in the art for an improved process for preparing such a composition possessing scuff and scratch resistance thus obviating the need for priming and painting processing steps. There is a further need for a composition having the capability to incorporate coloring pigments in order to obviate the need for painting of the exterior of articles formed from the composition.